#include <iomanip>
#include <iostream>
#include <numeric>
#include <vector>
using namespace std;
struct Item
{
    double unit_pirce;
    int units;
};

int main()
{
    vector<Item> v;
    for (Item item; cin >> item.unit_pirce >> item.units;)
    {
        v.push_back(item);
    }
    auto add_price = [](double p, const Item &i)
    { return p + i.unit_pirce * i.units; };
    double total = accumulate(v.begin(), v.end(), 0.0, add_price);
    cout << "总量：" << fixed << setprecision(2) << total << endl;
    return 0;
}